1. Field of the Invention
The subject invention is related to fluid filtration devices, and more particularly, to an apparatus and method for forming a spiral pleated filter cartridge.
2. Background of the Related Art
Cylindrical filter elements having radially extending longitudinal pleats are well known in the art and have been employed for many years to filter a wide range of fluids. Typically, because of the radial geometry of the pleats, there is a significant degree of spacing between adjacent pleat surfaces. Spiral pleated filter elements, which are also well known in the art, are designed so that adjacent pleats are laid-over upon one another so as to more effectively occupy the spacing between adjacent pleat surfaces, and thereby utilize more of the surface area of the filter material. Early examples of spiral pleated filters are disclosed in U.S. Pat. Nos. 2,395,449, 2,401,222 and 2,420,414 to Briggs and U.S. Pat. No. 2,801,001 to Bowers.
A more recent example of a spiral pleated filter element having laid-over pleats is disclosed in U.S. Pat. Nos. 5,543,047 and 5,690,765 to Stoyell et al. the disclosures of which are herein incorporated by reference in their entireties. The Stoyell et al. filter element comprises a three-layer composite of a filter medium, an upstream drainage layer disposed on the upstream surface of the filter medium, and a downstream drainage layer disposed on the downstream surface of the filter medium. The drainage layers are in the form of an extruded polymeric mesh oriented and configured so that opposing surfaces of adjacent pleats are in intimate contact with one another over a substantial portion of the length of the filter element.
The Stoyell et al. patents also disclose a method of forming a cylindrical filter element having radially extending pleats into a filter element having a plurality of laid-over pleats by placing the filter element over a cylindrical core disposed on a chuck, and thereafter placing a tubular member having an inner diameter which corresponds to the desired outer diameter of the laid-over filter element on the upper end of the filter element and pressing it downwards. As the tubular member moves downward, the pleats of the filter element are progressively laid-over against one another. When the entire length of the tubular member has been fit over the filter element, the tubular member, the core and the filter element are removed from the chuck and disposed on a second chuck. A cylindrical cage having an inner diameter corresponding to the desired outer diameter of the laid-over filter element is then placed on top of the tubular member and pressed downward until it completely displaces the tubular member from the filter element. The assembly, comprising the core, the laid over filter element and the cage are then removed from the second chuck and end caps are installed on both ends thereof.
The method disclosed in the Stoyell et al. patents is extremely labor intensive and the filters formed thereby are subject to random imperfection caused by manual misalignment of the various elements of the assembly. Accordingly, there is a need in the art to provide an apparatus and method for more efficiently and precisely forming a spiral pleated filter element.